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Re: Entering '<1' and 'BDL'

From: Tom Keller <kellert(at)ohsu(dot)edu>
To: Postgresql PDX_Users <pdxpug(at)postgresql(dot)org>
Subject: Re: Entering '<1' and 'BDL'
Date: 2010-04-20 19:49:50
Message-ID: (view raw or whole thread)
Lists: pdxpug
Why distinguish "below detection limit" at the data level? I would use the value measured and enforce the ramification of the detection limit in subsequent analysis. Then use NULL for missing values only.
 ... or isn't that feasible?


On Apr 20, 2010, at 12:38 PM, Rich Shepard wrote:

On Tue, 20 Apr 2010, Rich Shepard wrote:

The database we're building uses floating point numbers, where
appropriate. Spreadsheets use whatever someone wants to put in a cell. I
need to look at how NAN is expressed.

  However, this does raise a question that I need to answer: how to
distinguish between a sample taken, analyzed, and with a value below
detection limits and a sample not taken. There may be legitimate reasons for
not taking a sample, or it might have been missed inadvertently. Or, the
sameple might have been taken and analyzed but the results not entered in
the system.

  We need to ponder this.


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